Allow volumes from to be individual files

Fixes #4741
Right now volumes from expected a dir and not a file so when the drivers
 tried to do the bind mount, the destination was a dir, not a file so it
 fails to run.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add integration test for volumes-from as file
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add "test-integration-cli" to our DEFAULT_BUNDLES list (make all)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #4752 from crosbymichael/fix-volumes-from-files

Allow volumes from to be individual files
Merge pull request #4926 from tianon/add-cli-tests-to-default-bundles

Add "test-integration-cli" to our DEFAULT_BUNDLES list (make all)
split API into 2 go packages

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
split client in 2 files

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
fix tests

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
apply Reduce error level form harmless errors

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #4901 from vieux/split_api_2_pkg

Split API into 2 go packages
Make sure to set error reguardless of attach or stdin

Fixes #3364
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)